1. Field of the Invention
The present invention relates to synthesizing carbon nanotubes, and more particularly, to a method of synthesizing carbon nanotubes through local heating and an apparatus used for the same.
2. Description of the Related Art
It is known that a carbon nanotube is microscopically constituted such that a single carbon element is combined with three neighboring carbon atoms, a hexagonal ring is formed by the combination among the carbon atoms, and a plane composed of repeated hexagonal rings like a honeycomb is rolled to thereby form a cylindrical shape. The carbon nanotube is characterized by the diameter being usually several angstroms through several tens of nanometers, and the length being several tens through several thousands of times longer than the diameter. It is known that such a carbon nanotube has both metal property and semiconductive property, thereby having excellent physical and electrical properties. Accordingly, the carbon nanotube has been widely applied to a variety of fields using its conductivity and/or semiconductivity.
Conventionally, carbon nanotubes are synthesized by a method such as arc discharge method, a laser evaporation method, a thermal chemical vapor deposition (CVD) method, a catalytic synthesizing method or a plasma synthesizing method. These methods are performed at a high temperature of several hundreds through several thousands of degrees centigrade or under a vacuum to release the high temperature condition.
Moreover, in these conventional methods, an entire reactor is heated to meet a reaction temperature for synthesizing carbon nanotubes. Here, all substances such as reactant gases and a catalyst which are supplied into the reactor are heated. Accordingly, when a catalyst is loaded on a support or a substrate, the support or the substrate should be formed of a heat-resistant material which can tolerate a high reaction temperature as described above. In other words, selection of a support or a substrate for loading a catalyst is restricted.
To solve the above problems, it is a first feature of the present invention to provide a method of synthesizing carbon nanotubes, which allows a support or a substrate for loading a catalyst not to be heated to a high temperature by locally heating the catalyst.
It is a second feature of the present invention to provide a carbon nanotube synthesizing apparatus used for performing the above method.
Accordingly, to achieve the first feature of the invention, there is provided a method of synthesizing carbon nanotubes. In the method, a catalyst is introduced in a reactor, a reactant gas containing a carbon source gas is supplied over the catalyst, the catalyst in the reactor is locally and selectively heated, and carbon nanotubes are grown from the heated catalyst.
The local heating of the catalyst can be achieved by irradiation of microwaves, electromagnetic inductive heating, laser heating or radio frequency heating.
To achieve the second feature of the invention, there is provided an apparatus for synthesizing carbon nanotubes. The apparatus includes a reactor for receiving a catalyst, a reactant gas supplier for supplying a reactant gas containing carbon source gas into the reactor, and a local heater for selectively heating the catalyst received in the reactor.
The apparatus may also include a catalyst gas supplier for supplying the catalyst into the reactor in gas phase.
The local heater may include a microwave generator for generating microwaves, and a microwave guide connected to the reactor, the microwave guide guiding the microwaves to the reactor. The local heater may include a high-frequency coil installed around the reactor, and a power supply for applying high-frequency current to the high-frequency coil. The local heater may include a radio frequency generator installed near the reactor. The local heater may include a laser beam generator installed near the reactor, and a lens for focusing laser beams generated by the laser beam generator.
According to the present invention, carbon nanotubes can be synthesized under the condition of lower temperature, that is, in a state where the entire reactor is maintained at a low temperature, through local heating. Therefore, a substrate or a support for loading a catalyst thereon can be formed of polymer material or glass.